Constant line and speaker impedance volume control



Oct. 18, 1932. o, DQRAN 1,883,624

CON STANT LINE AND SPEAKER IMPEDANCE VOLUME CONTROL Filed May 24, 1929 Patented Oct. 18, 1932 UNITED STATES PATENT OFFICE LEROY '0. DORAN, CHICAGO, ILLINOIS, ASSIGNOB 'I'O CARTER RADIO COMPANY, OF

CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS oons'ran'r LINE AND SPEAKER 7 Application filed Kay 24,

My invention relates to volume control for speaker devices of radio sets, and more particularly to means for maintaining constant impedance "between the terminals of a speak er that is one of a number on the same receiving or amplifying circuit.

At the present time there is a tendency, particularly in hotelsand apartment houses, to equip the establishment with one or more receiving sets of high grade, and supplying of one speaker to a louder or lower volume causes a corresponding efli'ect upon the other and speakers inv parallel therewith, and thus makes it impossible to get reception of a constant volume.

One of the purposes of this invention is to provide a system whereby the tuning of the various speakers in parallel upon the circuit of a receiving or amplifyingdevice has little or no effect upon the impedance across the terminals of the receiving or amplifying device.

A further purpose is to provide, in such a system as has been described, means for also maintaining the impedance across the terminals of any particular s eaker substantially the same irrespective o the volume for which that speaker is tuned.

I will describe one form which my invention may take by reference to the accompanying drawing, wherein Fig. 1 is a plan view of a resistor element that is utilized in conjunction with each speaker to accomplish the result desired;

Fig. 2 is a section on the line 22 of Fig. 1;

Fig.3 is a wiring diagram showing the connections for a plurality of speakers in parallel to the output of an amplifying device.

mrnnancn vomnm oon'rnor.

1929. Serial no. 885,840.

Referring now in detail to the .drawing, I show at 5 the secondary-winding of the last stage of a radio receiving device, from which the conductors 6, 7 ,8 and 9, extend, as, for example, to diflerent suites of rooms in a building, these conductors being arranged in parallel.

Conductor 6 connects at 10 toone terminal of a resistance 11, the otherterminal of which is shown at 12 as having no direct connection to any other part ofthe circuit. A bridging memberyindicated generally by the numeral 13, and having three arms 14, 15 and 16, is adapted to connect the resitance 11 with two other resistances 17 and 18, as shown clearly in Fig. 3.

The circuit may then be traced from conductor 6 through resistor 11, arm 16, arm 14,

resistor 17 to conductor 19, which leads to one side of a loud speaker (not shown). The other terminal of the loud speaker is connected directly by means of the conductor 20 to the conductor 7, and is also connected by means of conductor '21 to the resistor 18. Conductors 8 and 9 are similarly connected, as shown, to resistors 11', 17 and 18', which resistors are adapted to be connected by a device 13 similar in all respects to that shown at 13. Conductors 19' and 20 lead to a second loud speaker in parallel with the first mentioned speaker.

Now, in the utilization of this device, let us assume that in one case the person listening to the first described speaker, which we will call for convenience sake speaker A, wants to turn the speaker down very low, while the person listening to the second speaker, or speaker B, desires to have the program brought in rather loudly. The connecting device 13 is turned by the operator of speaker A to the position shown, so as to completea circuit from conductor 6 through resistor 11, arm 16, arm 14, resistor 17, conductor 19, speaker A and conductorQO, back through conductor 7 to the opposite side of the transformer coil 5. At the same time,

a'parallel circuit which governs the amount through resistor 11, arm 16, arm 15, a small value across the speaker.

portion of resistor 18, conductor 21 and conductor 7. Thus it will be seen that the resulting voltage drop between the arm 16 at its contact point with resistor 11 and the conductor 7 will be only a small portion of the total drop across the transformer 5, and as the total drop across the speaker must be the drop between the arm 16, which isdirectconnected to arm 14, and the conductor 7, this drop must necessarily be the same small In the position shown, of course, this is greatly exaggerated, as it is unlikelythat, with the member 13 in the position shown, any one would be able to hear speaker A. 7

It will be noted, however, that the impedance across the line betweentheconduc- Y tors 6 and 7 is substantially equal to the value of one of the resistances 11, 17 or 18, which are made equal. This is due to the fact that arm 16 cuts ofl just as much resistance from resistor 11 in this circuitas arm 15 adds from resistor 18. I

At the same time, it will be noted that the total impedance between the conductors 19 and 20 leading to the loud speaker consists of substantially the same amount, namely, the greater portion of resistor 17 plus the small portion of resistor 18 which is encompassed by the circuit extending from conductor 19 through resistor 17, arm 14, arm 15, a'small'portion of resistor 18 and conductor 21, to conductor 20. l t

In speaker B the member 13' has been turned so as to bring .its arms in such position as to impress substantially the entire voltage between the terminals of the winding 5 across the terminals 19' and 20' of the loud speaker B. This is done, however, as is clearly apparent, without changing the value of the impedance connected across" conductors 8 and 9, or the value of the impedance connected across conductors 19 and 20'.

Thus it will be seen that the volume of the speakers may be regulated or adjusted in any manner that the user thereof desires without in any way'interfering with other speakers on the circuit or the tone of the in lvidual speaker, which is rather seriously afiected by variations .of impedance in its circuit.

The structure of resistors 11, 17 and" 18 and the member 13 with its corresponding arms 14, 15 and 16 is shown more clearl in Figs. 1 and 2, whereln, as shown, a dis 22 has an annular flange formed at the rim there'ofto provide a U-shaped recess at 28, into which an insulation strip 24 of similar shape is mounted, and the resistance stri 25 of insulating material, having woun thereon the'several resistances 11, 17 and 18, is clamped within these U-shaped mema central aperture at 29, in which a bearing sleeve is secured, and this sleeve may be mounted on a panel 31 by a suitable nut 32 being screw-threaded thereon to clamp the panel between the disk- 22 and the nut. A shaft 33 carrying a handle, 34 extends through the bearing sleeve 30 and has mounted thereon the three arms 14, 15 and 16, which contact with the resistors 11, 17 and 18, these three sleeves being connected together by being clamped upon the stub 35 projecting from the shaft 33 by means of a nut 36. The stub shaft 35 is, of course, flattened on the sides or otherwise made noncircular so as to hold the arms 14, 15 and 16 in proper position 120 apart. A spring bearing plate 37 is carried by the lowermost arm, so that these arms may be held against coming loose without tightening them to such an extent as to make it diflicult to turn the handle 34. Also a suitable stop, as shown at 38, is struck up from the disk 22 to limit the movement of the arms in both directions,

contacting when the member 13 is moved in one direction with arm 16, and when it is moved in the other direction with arm 14.

While I have described one specific form which the invention may take, it is obvious that various modifications may be made therein without departing from the scope of the invention, and it is to be understood that all such modifications are to be considered as art of this invention so long as they fall wit in the scope of the claim.

'Having thus described my invention, what I claim as new ters Patent is:

In a system of the character described including a reproducing device connected across the output circuit of radio receivin apparatus, means for varying the volume 0 said reproducing device without varying the impedance across the output circuit or reproducin device comprisin resistance units, an means for varying t e amount of said units in series with said reproducing device while maintaining a substantially constant amount thereof across the terminals of said device and a substantially constant amount thereof across the output circuit, said 4 last named' means comprising an adjustable contactor element having three contact making arms electrically connected to each ofllier and each engaging one resistance unit 0 y.

In witnesswhereof Ihereunto subscribe my name this 6 day of May, A. D1929.

- LEROY. O. DORAN.

clam ed within the U-shaped members 23 and with the strip 25. The disk 22 has 

